Actually it's the brilliance of YouTube and the internet. The security light came on on my 1999 Chevy Lumina. The mechanics I called quoted right at $300 (and the dealer $500) to fix the problem, which was changing the lock cylinder (which I can do but never have done).
When I checked on YouTube a bunch of guys said no, no, no, cut the orange wire under the dash (which goes to that crappy Vehicle Anti-Theft system), solder in enough resistors to match the resistor in the key, and you're done.
So I did it and the light went out. The car runs fine.
Cost: $10 for a 500 multipack of resistors, $5 for solder. I already had a $30 multimeter to test resistance and a cigarette lighter to melt solder.
Spent $15, save at least $285.
Without YouTube I would have had to pull the steering wheel and change the lock cylinder.